The present invention relates generally to packaging semiconductor integrated circuits, and more particularly to packaging a semiconductor sensor device that has lid and a mold compound formed over the lid.
Semiconductor packages are containers for integrated circuits and devices. The semiconductor package includes an integrated circuit formed on a semiconductor die. The semiconductor die is attached and electrically connected to a lead frame or substrate and then the semiconductor die and electrical connections are covered with a mold compound or encapsulant material to protect the die and the interconnections from moisture, electrical, physical, and other environmental forces and stresses. The I/O connections of the lead frame or substrate are exposed so that the semiconductor die can be connected to external circuitry such as when the semiconductor package is mounted to a printed circuit board (PCB).
Some semiconductor devices have a cavity formed within the packaged semiconductor assembly. For example, some semiconductor sensor devices require a cavity within the assembly for the functionality of the specific dies, such as sensor dies, like pressure sensor dies, g-cell or acceleration transducer dies, parameterized cell (p-cell) dies, temperature sensor dies, piezo resistive transducer (PRT) dies, optical sensor dies, light emitting/receiving dies, etc. For example, pressure sensor devices are not fully encapsulated to allow exposure to ambient environmental pressure conditions; however, the package must still protect the die from exposure to other environmental stresses and conditions.
Assembling such cavity package devices typically includes forming a cavity with a pre-molded lead frame and a lid attached to the lead frame, where a sensor die is mounted on the lead frame within the cavity and a gel is coated on the die prior to attachment of the lid to the lead frame. In such devices using pre-molded lead frames, where the cavity is formed by the mold itself, there is a possibility of gel leakage through micro-gaps that exist between the mold and the leads. This leakage of the gel can contribute to device defects and low production yields. Accordingly, such pre-molded cavity lead frames lack robustness.
Further, pre-molded lead frames are relatively expensive, adding to the cost of the packaged device. Also, sensor dies may experience parametric shifts during extreme environmental conditions imposed on the devices during processing and testing, for example by rapid decompression event (RDE) testing, where the packaged devices undergo rapid pressure drops to insure there is no bubble formation near the sensors, interfaces, and substrate.
Thus, there is a need for a cavity-type semiconductor device that addresses or at least alleviates some or all of the above problems.